Residual Mountains

Residual Mountains are formed from already existing mountains, which are lowered or reduced in size by agents of denudation such as running water, ice and wind. Therefore, Residual Mountains are the remains of already existing mountains. Residual Mountains are also called Mountains of Denudation.

After a Mountain has been formed its surface is continuously changing because it is constantly affected by external forces of nature. Running water, winds and ice cause erosion naturally on the surface of the mountain, over a long period of time, the height of the Mountain decreases and the size gets smaller. The degraded Mountains left after the denudation and erosion process are known as Residual Mountains.

Matterhorn in Switzerland, Girnar Hills, Nilgiri Hills, Mount Monadnock (USA), Highlands of Scotland, Highlands of Scandinavia, and Sierra of Spain are examples of residual mountains.

Denudation is a process that involves the wearing away of the Earth’s surface by various agents of erosion, such as wind, water, and ice.

Characteristics of Residual Mountains:

• Residual mountains are the remnants of previously existing mountains that have been subjected to weathering and erosion for an extended period.
• They have various heights and sizes due to erosion.
• The agents of denudation erode the soft rocks on the top of the mountain rapidly leaving the hard rocks behind.
• After the soft rocks are eroded the hard rocks (also known as bedrock) of the mountain is exposed.
• Their bedrock is usually either igneous or metamorphic rocks.

Formation of Residual Mountains:

Residual Mountains are formed from already existing Mountains, they may also formed from highly elevated landforms such as plateaux. These existing elevated landforms are lowered in height and size by agents of denudation such as running water, ice and wind. Residual Mountains are therefore the remains of already existing high mountains (or other highly elevated Landforms). After the reduction and erosion of the softer particles on the surface of the Mountain, the hard interior part of the Mountain which is highly resistant to erosion remains. This remaining part of the Mountain (or Landform) is a Residual Mountain.

The diagram below illustrates how resistant rocks become exposed on an elevated landform (e.g. a plateau) to become a Residual Mountain.

At times, resistant rocks form residual mountains called inselbergs.